The invention relates to conditioning of polishing pads.
Chemical mechanical polishing (CMP) is one accepted method of planarization. This planarization method typically requires that a substrate be mounted on a carrier or polishing head. The exposed surface of the substrate is typically placed against a rotating polishing disk pad or linearly belt pad. The polishing pad can be either a standard pad or a fixed abrasive pad. A standard pad has a durable roughened surface, whereas a fixed-abrasive pad has abrasive particles held in a containment media. The carrier head provides a controllable load on the substrate to push it against the polishing pad. A polishing slurry is typically supplied to the surface of the polishing pad. The polishing slurry includes at least one chemically reactive agent and can also include abrasive particles.
Over time, the polishing process glazes the polishing pad. The glazing phenomenon is a complex combination of contamination, thermal, chemical and mechanical damage to the pad material. When the polisher is in operation, the pad is subject to compression, shear and friction producing heat and wear. Slurry and abraded material from the wafer and pad are pressed into the pores of the pad material and the material itself becomes matted and even partially fused. These effects reduce the pad's roughness and its ability to apply fresh slurry to the substrate. The polishing pad surface is typically “conditioned,” whereby the polishing pad surface is deglazed removing trapped slurry, and unmatting or re-expanding the pad material. Conditioning is typically performed by scouring the polishing pad surface with an abrasive device such as a rotating diamond-coated disk.